Projecting apparatus



Jan. 8, 1929.

' W. H. HIRSCHFELD PROJECTING APPARATU S 3 Sheets-Sheet Filed July 11, 1923 WaZierHHiws 071 56212 Ina/anion- Jan. 8, 1929.

W. H. HIRSCHFELD PROJECTING APPARATUS Filed July 11, 1923 5 Sheets-Sheet -2 17272877120? mZi/er llb w' rsa ifeid.

Jan. 8, 1929. 1,698,096

w. H; HIRSCHFELD PROJECTING APPARATUS Filed July 11, 1923 3 Sheets-Sheet 3 R Ih/vei aifor."

WaZZeWHHZ'WSCFafGZd y viii/'95) Patented Jan. 8; 1929.-

UNITED STATES PATENT OFFICE.

WALTER H. HIRSOHFELD, BOSTON, MASSACHUSETTS, ASSIGNOR TO ROBERT II.

HOSMEB, OF BOSTON, MASSACHUSETTS/ PROJECTING APPARQTUS.

Application filed July 11,

This invention pertains to improvements in projecting apparatus, and more particularly, though not as to all its features exclusively, to improvements in light projecting apparatus of the reflecting arc type for use in motion picture projecting apparatus.

In the drawings,'which show a preferred form of one illustrative embodiment of my invention:

Figure 1 is a diagrammatic view illustrating the correct relative position between a given parabolic or spherical reflector, a given pair of carbon points of which the carbons are arranged with their axes substantially normal to the reflector, a given aperture in a film mask and suitable lens mechanism, which may of course vary in different types of machines, and the adjustment of which will be varied for projection under varying conditions;

Fig. 2 is a view similar to Fig. 1, showing I the ill effects of a slight maladjustment of the carbon points, particularly that carbon point which faces and projects the light upon the reflector;

Fig. 3 illustrates diagrammatically the position of a section through the light cone at the apertures in the film mask where the parts are in correct adjustment as shown in Fig. 1;

Fig. 4 shows the position of an adjacent section through the light cone at the aperture in the film mask where the carbon facing the reflector is slightly out of position relative to the reflector; Fig. 5 is a side elevation of a preferred form of light producing and projecting apparatus, primarily for use in connection with the projection of moving pictures and the like, being partly in section ona vertical central longitudinal plane;

Fig. 6 is a plan view, partlybroken away and partly in section on the line 66 of Fig. 5, illustrating a preferred form of apparatus for feeding the carbons toward one another automatically at a constant rate corresponding to the consumption of such carbons during use. It also shows preferred mechanism for bodily adjustment of the reflector in a direction toward and from the source of light and for angular adjustment of the reflector, laterally or vertically considered, or in any combination of the two;

Fig. 7 is a diagrammatic sectional view ilisaa. Serial no. 650,808.

Fig. 8 is a section through the rear carbon, I

which is preferably negative on direct current and is of course alternately positive and negative on alternating current, showing in cross-section a preferred form of carbon holder adapted to project the carbon through the center of thereflector;

Fig. 9 is a detail view, partly in vertical central section, showing a slip joint splined connection which permits vertical adjustment of the carbon and reflector carrying portion of the mechanism without corresponding movement of the actuator and other parts for automatically feeding the carbons; on line 9-9 of Fig. 6;

Fig. 10 illustrates a preferred form of front carbon holder;

' Fig. 11 shows on an enlarged scale a correct adjustment of the carbons and the resultant correct crater;

Fig. 12 shows a maladjustment of the carbons by spacing them too far apart and the resultant insufficient convexity of the crater;

Fig. 13 shows a maladjustment of the carbons by spacing them too close together and resultant excessive convexity of the crater;

Fig. 14 shows the too close proximity of the points necessary to correct the crater shown in Fig. 12; and

Fig. '15 shows the excess separation of the points necessary to correct the crater shown in Fig. 13.

Referring to the drawings and to the preferred embodiment of my invention selected for illustrative purposes, I have shown light projecting apparatus of the reflectin arc type includinga parabolic or spherical reflector 11 centrally apertured at 12 to admit-of the passage therethrough of a carbon 13 into juxtaposition to the end of a carbon 14, which is preferably somewhat larger than the carbon 13, so that light emanating from its end or crater ad acent the carbon 13 may-strike the face of the resible, being reflected from such face to focus at the film mask 15 in such manner that a cross-section of the cone of light at the film mask 15will, as nearly as may be, cut the corners of the film aperture 16, providing thereby maximum illumination throughout the entire area where the film is exposed to the light. If a section of the cone of light at this point is less than the diagonal of the rectangular opening, or of that portion of the film which is projected at any given time, the corners of the film will be poorly shown on the screen, while if a section of the cone of light at this point is substantially greater than such diagonal, the light will be unnecessarily diffused and the image of the film on the screen will be dimly illuminated. The lenses 17 may be of any suitable type, their adjustment relative to the film aperture varying in accordance with their curvatures and in accordance with the distance to the screen and the size of the projected image. In Figs. 1 and 2, I have not shown any change of the light rays by the lenses, but have projected the rays as though there were no lenses.

The initial relative position of the carbons 13, 14 and the relative position of the crater or source of light on the carbon 14 to the mirror 11 may be satisfactor ly provided by manual adjustment by observing the spot of light at the film aperture which is visible even when the light projecting apparatus is covered by the usual hood or housing. No sooner, however, is a correct adjustment of these parts secured, than the consumption of the carbons commences to produce an effective movement of the crater or source of light at the end of the carbon 14, such movement being in a direction away from the reflector 11. Such movement results (as ,is shown in Fig. 2) in a reduction of the crosssection of the cone of light at the film mask 15 and, assuming the correct adjustment illustrated in Fig. 1 has been initially provided, the gradual diminution of the cross-section of the cone at this point will very soon result in the corners of the film aperture not being covered by the direct cone of light (see Fig. 4), with resultant lack of illumination in the corners of the projected image.

, Even with constant attention, it is im- 7 practicable to maintain the correct relation composed. Ordinarily, the carbon 13 will be consumed at a rate of four as compared with a rate of three for the carbon 14, which is the larger .or front carbon, positive for direct current.

In practice, where the carbons are fed manually, the points of both carbons 13 and 14 are ordinarily initially set slightly too close to the reflector 11, thereby providing a cone of light of which the section at the film aperture will be considerably larger than such aperture, with resultant lack of perfect illumination of the projected image. As the carbons are consumed, the section of the cone of light at the film aperture will gradually reduce until the diameter of the sector corresponds to-the diagonal of the screen aperture and then, with further consumption, until such section becomes smaller than the screen aperture with resultant lack of illumination adjacent the corners of the projected image. During this period, the points ofthe carbons will have been gradually separating with resultant decrease in the amperage consumed and increase in voltage, and with that attendant malformation of the light projecting crater on the front carbon which always results from improper adj ustment of the points. Thus, even when the points are manually adjusted back to their initial position, the resultant projected cone of light will be less effective than where the adjustment is more constantly correctly maintained.

The formation of a satisfactory crater on that carbon from which the light passes to the reflector is dependent upon the maintenance of the proper gap between the carbons. If the carbons are adjusted too closely together, the crater will become too deep (as shown in Fig. 13) and a formation of silicate will be likely to take place on the point of the rear or negative carbon, which will obstruct the light. As the carbons burn and become too far separated, the point of the negative carbon will become more and more blunt, while the crater will become more and more shallow (as shown in Fig. 12); rNot only will the shallow crater give forth less light, and not only will the positioning of the car.- bons which produces the crater of insuflicient depth result in an improper cone of light on the screen aperture, but, even when the points after being too far' apart, are again fed back to what would otherwise be their proper distance apart, an improper adjust"- ment will be provided which will give such an unsatisfactory lighting of the projected image that it will be necessary again to adjust the carbons into a more or less improper relation in order'to. clarify somewhat the projected image, and therefore the malformation, once produced, will in practice he very likely to be continued indefinitely unless it be corrected by such an adjustment as will for the time being at least result in an imperfect illumination of the image pending the formation of a proper crater. Y

A proper crater is shown in Fig. 11, and the positions for correcting the improper craters of Figs. 12 and 13 are illustrated in Figs. 14 and 15 respectively, each of the latter positions, however, resulting in improper illumination of the projected image from the film, which is adjacent the film opening 16, in the film screen 15. The formation of the crater on the front carbon will be generally the same for alternating as for direct current, though carbons for differing currents may vary somewhat in that the central or core portions thereof, usually softer than the exterior port-ions, may vary in degree of hardness or softness.

While the carbons are in substantial alignment, it is desirable to locate the axis of the carbon providing the crater at a little higher level than the cooperating carbon, so that the tendency of the heated gases to rise will not cause the crater to be formed above the center of its carbon.

In the specific embodiment of my invention illustrated, the rear or negative carbon 13 is carried by a sliding support 21 movablelongitudinally of guide rods 22, 23 by a screw 24, while the front or positive carbon 14 is carried by a support 26 movable longitudinally of said guide rods 22, 23 by a screw 27, which may be and preferably is coaxial with and rigidly connected for rotation to the screw 24, being of opposite hand therefrom and'of such different pitch as will result in a differential feeding of the carbons proportionate to their different rates of consumption.

An initial adjustment of the carbons to their proper relation to each other and to the reflector 11 may be procured by adjusting the carbon 13 in a holder tube 28 adapted to grip and release the carbon as such tube is'moved forwardly or rearwardly in the sleeve 29 by adjustment of the screw 30, which may be used to provide a fine adjustment of the carbon. In lieu of this adjustment, the carbon, the tube 28 and the sleeve 29 may be bodily moved forwardly or rearwardly pursuant to loosening of the clamping screw 31. The sleeve 29 present-s inwardly sloping cam surfaces at 32 adjacent its forward end, and grip 01' release of the carbon 13 is effected as the tube 28, which is longitudinally slotted adjacent its forward end (as best shown in Fig. 8) is crowded against or drawn away from the sloping cam. surfaces 32, thereby providing a very satisfactory electrical con tact.

The initial adjustment of the carbon 14 may be effected by loosening the screw 33 carried by the ring 34, thereby releasing the carbon which is clamped between a carbon jaw 35 swiveled to the end of the screw 33 and a carbon jaw 36 carried by a relatively thin stationary support 37. The main support for the jaws is located entirely without the cone of light, being preferably a ring 34 of such diameter as not to cut the cone of light thrown by the reflector. The supports 33 and 37 and the carbon clamping jaws 35 and 36 are all of relatively light but strong construct-ion, so that as little obstruction as practicable of the cone of light will be effected while holding the carbon in the center thereof. Lateral adjustment of the carbon point may be effected by swinging the carbon ring 34 about the axis of a vertical carrying pivot entered in the sleeve 38 (Fig. 10), and vertical adjustment may also be secured at this point.

When the initial rough manual adjustment has been secured, the current may be turned onto the carbons and, pursuant to disengagement of the automatic constant feed mechanism, hereinafter more fully described, by releasing the clutch 40, the carbons may be moved into contact to start the arc by manually turning the handle 41 on the rear end of the shaft which provides the screws 24 and 27, rotation of which moves the carbons toward or from one another. After the arc is established by contact, the points are spread somewhat by turning. the handle 41 and connected parts in reverse direction pursuant to which the clutch nut threaded on the rear end of the shaft 42, carrying the handle 41, is turned to press the worm gear 43 into contact with the shoulder 44 on the carbon-feeding shaft,

thereby effecting a connectionof the carbon feed shaft with a train of gearing including the worm gear 43, the worm 45 keyed to a shaft 46, which has a splined connection with the sleeve 47 connected to the shaft 48, to which is secured worm gear 49 in turn is driven by the worm 50 on the shaft 51 carrying gear 52 engaged by a pinion 53 on the shaft of the motor 54. Thus, when the motor 54 is energized, the pinion 53 will drive the gear 52 and its carrying shaft 51 at a somewhat slower rate of speed than the motor shaft, the worm 50 cooperating with theworm gear 49 efiecting a second speed reduction,

and the worm 45 cooperating with the worm gear 43 effecting a third speed reduction, so that the carbon-feeding shaft will move at a very slow rate of speed.

It will be understood that the before described chain of gearing may be altered for varying conditions. I prefer, however, somewherein the train of mechanism to provide an opportunity for a fine adjustment of the motor speed, which fine adjustment may take the form of a governor brake, which, in the form of my invention illustrated, includes a hub 60 pinned to theshaft 51, a. discfil slidably mounted upon said shaft 51, and spring governor arms connecting the hub 60 and disc 61 with governor weights 63 carried by the spring 62, so that,

35 metal.

as the shaft 51 revolves, the centrifugal force, acting on the weights 63, will force apart the springs 62, thereby drawing the disc 61 toward the hub 60 and against an adjustable 5 brake element 70, which may be a felt pad carried by a lever 71 fulcrumed at 72 and presenting a rearwardly extending portion 73 adj ustably engaged by a screw 74.

Assuming that the crater on the carbon 0 point is once correctly formed, and that the motor 54 rotates at approximately the correct speed in accordance with the gear reduction provided, I prefer that the carbon points be fed toward one another at a rate slightly greater than their rate of consumption, but

that this rate of feed be reduced by the fine adjustment to the exact rate of feed required. This is effected by slowing down the motor by loading it frictionally from the governor disc 61 by adjustment of the screw 74 so that the exact desired rate of feed of the carbons is provided.

The carbons, their brackets and their guide supports 22, 23 are preferably all supported by a cradle 80, which also carries the feed screws and other mechanism hereinafter described. The cradle 80 is adjustable vertically by suitable screwed connection with the carrying base 81, such connection preferably 30 taking the form of a screw provided with a nut 82, such screw entering in a threaded recess above thebed plate 81. The cradle 80 and 4 through of the various feed and adjustment rods. It is desirable to locate the actuating motor for the carbon feed exterior to this hood and therefore such motor cannot well be carried by the cradle 80. The sp-lined connection (illustrated in Fig. 9) between the worm gear 49 and the worm 45 permits limited vertical adjustment of the cradle relative to its base and also relative to the motor 54 without interruption of the train of gearing from the latter.

To admit of angular adjustment of the reflector 11, I have provided for the support thereof a frame 90 having at its bottom a ball 91'engaged in a suitable ball and socket 55 recess in the clamping support 92, which may be held atthe desired elevation on the supporting stud 93 by the screw 94. The clamping support 92, 92' may grip or release the ball by tightening or loosening a screw 95 having a relatively long handle 96 extending exteriorly of the hood or housing which protects the apparatus. I have found that, while under ideal conditions no angular adjustment of the reflector 11 would be necessary, that it is practically impossible to sehas been found desirable to correct this error by appropriate movement of the reflector. This adjustment of the reflector must take place while the carbons are energized, and I have therefore provided mechanism for eflecting such adjustment from the exterior of the hood or housing. I have found by experiment that a very accurate and well controlled adjustment may be efi'ected by applying the mirror moving force at the ball and socket connection thereof and to this end I have provided a handle 98, of which the rear end extends outside the hood or housing and of which the front end connects with the ball 91 at the bottom of the mirror support. Thus, by slightly loosening the clamping screw 95 and appropriate movement of the reflector controlling handle 98, the light cone may be centered upon the film aperture 16 very accurately, being then held there by tightening of the clamping screw 95. Ordinarily forany given moving picture installation, it is not necessary to adjust the mirror bodily to any great extent toward or. from the film aperture, but to permit of such adjustment for varying conditions in the different installations, and to permit of very slight adjustment of the mirror to compensate for possible errors in the initial setting of new carbons, I have provided a reflector adjusting screw 100 passing through a threaded hole in the mirror support 101, the latter conveniently being guided and supported by the same guide rods 22, 23 which guide and support the carbon holders 21 and 26. Adjustment of the mirror may thus be conveniently effected by rotation of a handle 103 preferably connected by a universal joint 104, to the reflector feed screw 100.

The specific mechanical construction of the mechanism hereinbefore described may of course be greatly varied while preserving the most important, features of my invention, namely, the maintenance of a substantially constant and unchanging ideal light condition at the film aperture, the mainte nance of such condition being primarily dependent upon the maintenance of a proper crater at the front carbon and the constant maintenance of a proper relation bet-ween this crater and the reflector 11. The ease of adjustment, flexibility, convenience and accessibility provided by the various parts are, however, of great importance, which will be appreciated by bearing in mind that the unbroken continuityofthe-performance as well as the uniformity and high quality of the projected images is necessary to maintain the undivided-attention of the spectators at a moving picture show.

While I have shown and described a preferred embodiment of my invention, it will be understood that major changes involving omission, substitution, reversal of parts, and even changes in the mode of operation may be maderwithout departing from the scope of my invention, which is best defined in the following claims. 7

I claim: I

1. Moving picture projecting apparatus comprising, in combination, a screen providing a film aperture, a concave reflector, two carbons for providing an are located between said reflector and said aperture, said carbons generally axially aligned between said reflector and said aperture and positioned to provide a cone of light of which a cross-section at said film aperture will circumscribe the corners of said film aperture, automatically operating power driven means associated with said carbons for moving them toward one another at a rate slightly greater than the rate of consumption thereof, and a governor cooperating with said power means to decrease the speed of said power means to a rate substantially equal to the rate of consumption of said carbons.

2. Moving picture projecting apparatus comprising, in combination, a screen providing a film aperture, a concave reflector, two carbons for providing an are located between said reflector and said aperture,

. said carbons generally axially aligned between said reflector and said aperture and positioned to provide a cone of light of which a cross-section at said film aperture will circumscribethe corners of said film aperture, power means having the capacity for moving said carbons toward one another at a rate slightly greaterthan the rate of consumption thereof, and a centrifugal governor cooperatin with said power means to decrease the spec of said power means to a rate substantially equal to the rate of consumption of said carbons.

3. Moving pictureprojecting apparatus, comprising in combination, a screen providing a film aperture, a concave reflector, two carbons for providing an are located between said reflector and said aperture, said carbons generally axially aligned between said reflector and said aperture and ositioned to provide a cone of light of which a cross-section at said film aperture will circumscribe the corners of said film aperture, power means having the capacity for moving said ,c'arbons toward one another at a rate slightly greater than the rate of consumption thereof, and a governor operating a friction cooperating with said power means to defor said feeding means, mounted independ ently of said cradle, and a slip joint operatively interposed in the train of mechanism connecting said prime mover and said screw mechanism to admit of Vertical adjustment of said cradle without corresponding movement of said prime mover.

5. Picture projecting apparatus comprising, in combination, a source of light, a reflector, a support for said reflector and a ball and socket joint interposed between said reflector and said support to permit angular adjustment of said reflector relative to the source of light, a housing surrounding said source of light and reflector, and a handle connected to said ball and extending exteriorly of saidhousing for adjusting said mirror by adjustment of said ball in its socket.

6. Picture projecting apparatus comprising, in combination, a source of light, a reflector, a support for said reflector and a ball and socket joint interposed between said reflector and said support to permit angular adjustment of said reflector relative to the source of light, a housing surrounding said source of light and reflector, and a handle connected to said mirror and extending exteriorly of said housing, said handle connected directly to said ball of said ball and socket joint.

7 Moving picture projecting apparatus comprising, in combination, a screen providing a film aperture, a concave reflector, two carbons for providing an are located between said reflector and said screen, said carbons being generally axially aligned along the axis passing between said reflector and the film aperturerin said screen, continuously operating motor driven carbon feeding means operatively connected to the carbons and motor speed governing means operatively controlling the speed of the motor with relation to the desired space between the two carbons, whereby one carbon is fed toward the other at'a rate to provide a crater of substantially uniform concavity in one of said carbons from which is reflected a beam of light of substantially constant cross-section at the aperture in said screen. i

' 8. Moving picture projecting apparatus including a screen providing a film aperture, a reflector, an arc li ht comprising two carbons enerally axially aligned, a crater presente by one of said carbons which faces the end of the other carbon, carbon-supporting 'means, continuously operating power driven feeding means connected with the carbonsupporting means and carbon feed-controlling means operating in conjunction with the arc gap to control the speed at which the carbon-feeding means may be driven, thereby to provide for feeding said carbons toward each other at a rate of speed substantially equal to their rate of consumption for maintaining said crater at a substantially uniform concavity.

' 9. Moving picture apparatus including a screen rovidin a film a rture a reflector an are light comprising two carbons one of which presents a crater facing said reflector, continuously operated carbon-feeding means, operatively connected to said carbons and governing means operating in conjunction with the arc gap, said governing means being operatively connected with the means for feeding the carbons to control the speed thereof, whereby the feeding of the carbons is controlled to maintain sald crater at a substantially uniform concavity.

In testimony whereof, I have signed my name to this specification. 

